Adsorption and leaching of fluorotelomer compounds and perfluoroalkyl acids in aqueous media by activated carbon prepared from municipal biosolids.

Perfluoroalkyl acids (PFAAs) are ubiquitous in nature and pose serious health risks to humans and animals. Limiting PFAA exposure requires novel technology for their effective removal from water. We investigated the efficacy of biosolid-based activated carbon (Bio-SBAC) in removing frequently detected PFAAs and their precursor fluorotelomer compounds at environmentally relevant concentrations (∼50 µg/L). Batch experiments were performed to investigate adsorption kinetics, isotherms, and leachability. Bio-SBAC achieved >95% removal of fluorotelomeric compounds, indicating that the need for PFAA removal from the environment could be minimised if the precursors were targeted. Kinetic data modelling suggested that chemisorption is the dominant PFAA adsorption mechanism. As evidenced by the isotherm modelling results, Freundlich adsorption intensity, n-1, values of <1 (0.707-0.938) indicate chemisorption. Bio-SBAC showed maximum capacities for the adsorption of perfluorooctanoic acid (1429 µg/g) and perfluorononanoic acid (1111 µg/g). Batch desorption tests with 100 mg/L humic acid and 10 g/L NaCl showed that Bio-SBAC effectively retained the adsorbed PFAA with little or no leaching, except perfluorobutanoic acid. Overall, this study revealed that Bio-SBAC is a value-added material with promising characteristics for PFAA adsorption and no leachability. Additionally, it can be incorporated into biofilters to remove PFAAs from stormwater, presenting a sustainable approach to minimise biosolid disposal and improve the quality of wastewater before discharge into receiving waters.

Removal of perfluoroalkyl acids from aqueous media by surfactant-modified clinoptilolites.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are environmentally persistent, bioaccumulating, and toxic compounds that have attracted global attention. It is challenging to reduce the residual concentrations of these compounds to safe discharge limits. In this study, batch experiments were performed to evaluate natural clinoptilolite and clinoptilolites modified (MC) with cetylpyridinium chloride (CPC-MC), didodecyldimethylammonium bromide (DDAB-MC), hexadecyltrimethylammonium bromide (HDTMA-MC), and tetramethylammonium chloride (TMA-MC) as cost-effective aqueous PFAS adsorbents. The removal capacities of the adsorbents for the majority of the PFASs decreased in the following order: DDAB-MC > CPC-MC ≫ modified natural clinoptilolite with hexadecyltrimethyl ammonium bromide (HDTMA-MC) ≫ modified natural clinoptilolite with tetramethylammonium chloride (TMA-MC) ≈ natural clinoptilolite modified with NaCl (NC). In particular, CPC-MC and DDAB-MC reduced PFASs concentration in 50 µg/L by up to 98% for perfluorooctane sulphonate. Within 30 min, CPC-MC (30.5 µg/L) and DDAB-MC (32.1 µg/L) met the PFOS water quality criterion of 36 µg/L in inland surface waters. Both adsorbents met this criterion at the highest solution volume (40 mL) and 0.125 g/L (solid-to-liquid ratio of 1:8). PFASs with short hydrocarbon chains competed more for adsorption. PFASs with sulphonate functional groups were also adsorbed more than carboxyl groups in single- and multi-PFAS solutions. The modified surfaces of clinoptilolites controlled PFAS adsorption through hydrophobic and electrostatic interactions. PFAS removal with surfactant-modified clinoptilolites is cost-effective and protects aquatic environments by using surplus natural materials.

Co-pyrolysis of sewage sludge and biomass waste into biofuels and biochar: A comprehensive feasibility study using a circular economy approach.

Enormous annual sewage sludge (SS) volumes pose global environmental challenges owing to contamination and significant greenhouse gas emissions. Here, we investigated the economic viability of co-pyrolyzing SS and biomass waste to produce biofuels (bio-oil and gas) and biochar. Net present worth (NPW) analysis, the sale product break-even price, and sludge handling price (SHP) were used to determine the profitability of co-pyrolysis compared with SS pyrolysis alone and conventional treatment methods. In this study, the sale prices of biochar based on quality (i.e., stability, carbon sequestration effectiveness, and heavy metal content) were estimated to be 2.24, 1.44, and 0.98 CAD/kg for high-, medium-, and low-grade biochar. The bio-oil prices, estimated based on the higher heating values of bio-oil and diesel, ranged from 0.80 to 1.22 CAD/kg. Sawdust (SD) and wheat straw (WS) were the chosen co-pyrolysis feedstocks, with four mixing ratios (20, 40, 60, and 80 wt%). Economically, SD (40 wt% mixing ratio) co-pyrolysis achieved the best performance, with a maximum NPW of 8.71 million CAD. SD single and co-pyrolysis were the only profitable scenarios. Moreover, SS single pyrolysis and WS co-pyrolysis exhibited higher profitability than conventional SS treatment methods, with SHPs of 65 and 40 CAD/1000 kg dry sludge, respectively. Sensitivity analysis highlighted the dependence of economic performance on biochar and bio-oil market value. This study offers the first economic analysis of this approach and enhances our understanding of the potential of co-pyrolysis for biofuel and biochar production, providing innovative solutions for the environmental challenges of SS disposal.

A comparative life-cycle assessment and cost analysis of biofilters amended with sludge-based activated carbon and commercial activated carbon for stormwater treatment.

Environmental and economic issues resulting from the unsustainable management of sewage sludge from wastewater have necessitated the development of eco-friendly sewage sludge disposal methods, whereas stormwater effluent contains tremendous amounts of pollutants. This study compares the feasibility and environmental impacts associated with incorporating biofilters with sludge-based activated carbon (SBAC) versus commercial activated carbon (CAC) for stormwater treatment. The results demonstrate that the construction and disposal life-cycle stages are the dominant contributors to several environmental impact categories, including resource scarcity, carcinogenic toxicity, terrestrial ecotoxicity, and ozone formation indicators. Across multiple impact categories, the incorporation of biofilters with SBAC can reduce the negative environmental impacts associated with biofilter construction and disposal by 40% over a 50-year analysis period. In contrast, the most significant improvement is on construction-dominant indicators, where the decreased need for biofilter reconstruction results in a higher reduction in environmental impacts. Economically, amending the biofilter with SBAC can increase profits by up to 66% due to extending its lifespan. This study shows that SBAC has similar performance as CAC for lowering the negative environmental impacts resulting from biofilter construction, while increasing the overall net profits of the system. However, converting sewage sludge to an effective sorbent (SBAC) and incorporating SBAC into a biofilter to capture pollutants from stormwater is an economically and environmentally sustainable solution available to practitioners to manage sewage sludge and stormwater effluent. This solution protects the environment in a cost efficient, sustainable manner.

Using circular economy principles in the optimisation of sludge-based activated carbon production for the removal of perfluoroalkyl substances.

Massive sewage sludge (SS) production from municipal wastewater treatment plants and the presence of numerous pollutant types render the process of SS treatment and disposal costly and complex. Here, resource recovery from SS was maximised via the optimisation of sludge-based activated carbon (SBAC) production for the removal of poly- and perfluoroalkyl substances (PFASs), while considering economic factors and minimising environmental impacts. SBAC production optimisation was realised under different operating conditions (different ZnCl2 impregnation ratios and different pyrolysis activation temperatures and durations). The sorption capacity of the optimised SBAC with respect to the removal of nine commonly detected PFASs, with environmentally relevant concentrations (∽50 µg/L), from simulated wastewater was evaluated. Economic analysis and life-cycle assessment (LCA) were also performed to determine the feasibility of the process and its potential role in the circular economy. Batch adsorption tests confirmed the high efficiency of the optimised SBACs for PFAS removal (93-100 %), highlighting the possibility of converting SS to SBAC. Economically speaking, the optimised SBAC at 1.5 M ZnCl2, 500 °C, and 0.75 h reduced total production cost by 49 %. Further, the cost could be reduced to as little as 1087 US $/metric-ton compared with that corresponding to the original conditions (2.5 M ZnCl2, 500 °C, 2 h; 2144 US $/metric-ton). LCA results also showed that freshwater ecotoxicity, marine ecotoxicity, and human non-carcinogenic toxicity were the most affected environmental impact indicators, showing a 49 % decrease when ZnCl2 impregnation ratio was reduced from 2.5 to 1.5 M. These findings highlighted the optimal conditions for the production of SBAC with high sorption capacity at a reduced cost and with reduced environmental impacts. Thus, they can serve as valuable tools for decision making regarding the selection of the most sustainable and economically feasible process for PFAS removal.

Antibacterial Activity of a Natural Clay Mineral against Burkholderia cepacia Complex and Other Bacterial Pathogens Isolated from People with Cystic Fibrosis.

There is an impending crisis in healthcare brought about by a new era of untreatable infections caused by bacteria resistant to all available antibiotics. Thus, there is an urgent need to identify novel antimicrobial agents to counter the continuing threat posed by formerly treatable infections. We previously reported that a natural mineral clay known as Kisameet clay (KC) is a potent inhibitor of the organisms responsible for acute infections. Chronic bacterial infections present another major challenge to treatment by antimicrobials, due to their prolonged nature, which results in repeated exposure to antibiotics and a constant selection for antimicrobial resistance. A prime example is bacteria belonging to the Burkholderia cepacia complex (Bcc), which particularly causes some of the most serious chronic lung infections in patients with cystic fibrosis (CF) associated with unpredictable clinical outcomes, poor prognosis, and high mortality rates. Eradication of these organisms from CF patients with limited effective antimicrobial options is a major challenge. Novel therapeutic approaches are urgently required. Here, we report the in vitro antibacterial activity of KC aqueous suspensions (1-10% w/v) and its aqueous extract (L100) against a collection of extensively and multi-drug resistant clinical isolates of Bcc, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia isolated from patients with CF. These findings present a potential novel therapy for further investigation in the clinic.

Microplastic removal from urban stormwater: Current treatments and research gaps.

Stormwater is a major contributor to microplastic (MP) pollution in the aquatic environment. Although MPs are associated with many toxicological effects, their levels in stormwater are not regulated. This review compared the effectiveness of different MP removal technologies from stormwater runoff and examined the performance of typical stormwater treatment systems for MP removal to assess possible MP pollution control via stormwater management. Bioretention and filtration systems performed similarly with 84-96% MP removal efficiencies. Despite the limited number of studies that focused on wetlands and retention ponds, preliminary data suggested potential for MP removal with efficiencies of 28-55% and 85-99%, respectively. Despite the higher efficiency of bioretention and filtration systems, their removal efficiency of fibrous MPs was not optimal. Furthermore, wetlands were less effective in removing MPs than retention ponds, although the limited data might lead to an inaccurate representation of typical performances. Therefore, more research is required to arrive at definitive conclusions and to investigate alternative treatment options, such as ballasted sand flocculation, flotation, and biological degradation, and evaluate the effectiveness of bioretention and filtration for MPs <100 µm.

Adsorption of p-benzoquinone at low concentrations from aqueous media using biosolid-based activated carbon.

The toxic oxidation intermediate p-benzoquinone exists in aqueous environments at dilute concentrations above the fish-toxicity limit of 0.045 mg/L, affecting aquatic life. The reduction of this compound to the concentrations required to achieve safe discharge limits is challenging. In this study, the adsorptive removal of p-benzoquinone by a biosolid-based activated carbon (SBAC) was systematically investigated in batch experiments. The adsorption rate was rapid, and the bulk of p-benzoquinone adsorption occurred within 30 min. The maximum adsorption capacity of SBAC was estimated at 19.6 mg/g using the Langmuir isotherm model. Its adsorptivity was independent of temperature from 6 to 40 °C. The presence of 6 g/L of chloride and 500 mg/L of sulphate did not affect the removal of 1 mg/L p-benzoquinone, whereas 15 mg/L of humic acid media slightly decreased the p-benzoquinone removal from 87.0% to 83.2%. Diffusion, hydrophilic, and electrostatic interactions (i.e., dipole-dipole) govern the adsorption of p-benzoquinone and are influenced by the SBAC surface chemistry. Biosolid-based activated carbon can lower the residual p-benzoquinone to below the fish-toxicity limit of 0.045 mg/L within 1 h of sequential adsorption. Thus, biosolid-based activated carbon can effectively remove p-benzoquinone from aqueous environments; this is a waste-to-resource approach that addresses sustainability (waste disposal) and environmental protection (pollutant removal).

Biosolids-based activated carbon for enhanced copper removal from citric-acid-rich aqueous media.

In this study, we employed batch experiments to assess the effects of citric acid on the Cu(II) removal efficiencies of seven biosolids-based adsorbents. The adsorbents used were dried biosolids (BS), biosolids biochar (BSBC), biosolids-based activated carbon (SBAC), nitric-acid-modified BSBC (BSBC-HNO3) and SBAC (SBAC-HNO3), and amine-modified BSBC (BSBC-NH2) and SBAC (SBAC-NH2). However, with 100 mM citric acid in 1 mM Cu(II) solution, only SBAC showed an increase in Cu(II) removal efficiency (64.0-93.5%). Therefore, we used SBAC for further optimisation of the adsorption process. The kinetics data, optimally described by the pseudo-second-order model, indicated that bulk Cu(II) adsorption occurred within 10 min. The highest Cu(II) removal was at pH 3, with the estimated maximum Cu(II) adsorption capacity of SBAC increasing from 0.14 to 0.30 mmol/g, with 100 mM citric acid present. This result clearly indicated the positive effect of citric acid on Cu(II) adsorption. With citric acid present, the Freundlich model optimally fitted the adsorption isotherm data, suggesting adsorption of Cu(II) in multilayers. Further investigation of Cu(II) adsorption in a sequential setup proved that SBAC could lower the residual Cu(II) in the solution to below the discharge limit (0.05 mM) in 1 h. Overall, the production of activated carbon from BS has been proven an efficient Cu(II) adsorbent for Cu-citric-acid-rich aqueous media as a simulation of real wastewaters/leachates, as well as achieving waste-to-resources goals. This is the first study to identify an adsorbent (SBAC) with increased Cu(II) adsorption capacity in the presence of excess citric acid.

Sludge-based activated carbon and its application in the removal of perfluoroalkyl substances: A feasible approach towards a circular economy.

This study explores the recovery of resources and energy from sewage sludge through the production of sludge-based activated carbon (SBAC) considering circular economy principles. The SBAC production costs were estimated under three scenarios considering various sludge dewatering/drying schemes to determine the production feasibility and its role in the circular economy. SBAC was tested in the removal of a mixture of nine commonly detected poly- and perfluoroalkyl substances (PFASs) in environmentally relevant concentrations of ∽50 µg/L in comparison to commercially available activated carbon (AC) using 5 mg of sorbent and 5 mL of a nine-PFAS mixture in deionised water. SBAC can be produced at approximately 1.2 US $/kg, which is substantially lower than the average production cost of commercial AC of >3 US $/kg. A net revenue ranging from 2 to 7 US $/kg SBAC was estimated by recycling the produced non-condensable gases and bio-oil to produce energy and selling the SBAC. Batch adsorption tests showed that the PFASs removal of SBAC was superior to that of granular AC and similar to that of powdered AC, reaching >91% to below the detection limit. The kinetics tests revealed that adsorption by SBAC and AC occurred within 15 min. The overall results demonstrate the potential of SBAC as an effective sorbent for PFASs, achieving waste-to-resources circular economy via resource and energy recovery from sewage sludge, eliminating sludge disposal and contaminant-leaching to the environment, and in enhancing the quality of wastewater effluent before discharge.

Exploratory study of removing nutrients from aqueous environments employing a green synthesised nano zero-valent iron.

This study explores the green synthesis of nano zero-valent iron (nZVI) extracted from the peel of selected waste fruits: banana (BP), mango (MP), and pomegranate (GP), for the removal of nutrients from aqueous environments. The extract was prepared by heating de-ionised water at 60°C for 5 min, adding a reducing and a stabilising agent, FeCl3, then stirring with a N2 gas flush solution to form iron nanoparticles, with a final drying step under N2 conditions. Using a variety of characterisation techniques, it was determined that nZVI particles were successfully synthesised via the reduction of iron (III) to iron (0) and stabilised by the presence of phenolic compounds in the extract. The removal of 20 mg/L nutrients from an aqueous solution carried out using the nZVIs resulted in nitrate removal of 92% (nZVI-GP), 88% (nZVI-BP), and 72% (nZVI-MP) within 5 min, whereas ∼98% phosphate was removed by all three nZVIs within 60 min. The aging effect was also tested. Aging the nZVIs for >20 days resulted in less efficient phosphate adsorption after exposure for 250 min; ∼70% phosphate removal was achieved using the nZVIs under these conditions. The mechanisms and pathways of nitrate reduction, including the adsorption of phosphate by nZVI were demonstrated, and discussed. Leachability tests of the phosphate-loaded nZVIs revealed that 10%, 28%, and 48% phosphate was released from the nZVI-GP, nZVI-BP, and nZVI-MP particles, respectively. Using waste fruit is, therefore, a viable and sustainable alternative to the traditional sodium borohydride method to produce nZVIs for environmental application.

Adsorption of polycyclic aromatic hydrocarbons by surfactant-modified clinoptilolites for landfill leachate treatment.

The authors report the potential adsorption capacities of three surfactant-modified clinoptilolites (MC)-cetylpyridinium chloride (CPC)-MC, didodecyldimethylammonium bromide (DDAB)-MC, and hexadecyltrimethylammonium bromide (HDTMA)-MC-for the removal of polycyclic aromatic hydrocarbons (PAHs) from aquatic environments and landfill leachate. A liquid-liquid extraction method was used to extract PAHs from water and GC/MS was used to analyse the PAHs. PAH accumulations on CPC-MC, DDAB-MC, and HDTMA-MC were linear over 21 successive batch adsorption tests for anthracene (708, 737, and 750 µg/g), fluoranthene (1355, 1583, and 1303 µg/g), fluorene (973, 1060, and 1147 µg/g), phenanthrene (844, 1057, and 989 µg/g), and pyrene (1343, 1569, and 1269 µg/g). The leachability after 21 successive accumulations was <2% for anthracene, <4% for fluoranthene, <3% for fluorene, <4% for pyrene, and <5% for phenanthrene for each adsorbent. PAH removals from landfill leachate for anthracene, fluoranthene, fluorene, phenanthrene, and pyrene were 97.8%, 98.6%, 95.7%, 97.0%, and 98.5% for CPC-MC and 99.0%, 99.6%, 98.0%, 99.0%, and 99.6% for DDAB-MC, respectively, meeting the fresh water quality standards established by British Columbia and the World Health Organization (WHO) for anthracene, fluoranthene, and fluorene. The molecular weight and molecular structure of PAHs and the hydrophobicity of adsorbents can fundamentally influence the PAH adsorption mechanism based on π-π stacking.

Exploring indirect photolysis of 6:2 fluorotelomer sulfonate in landfill leachate under simulated sunlight: effect of humic acid and nitrate.

Landfill leachate is exposed to sunlight through on- and off-site leachate treatment and disposal to surface water bodies. Very little is known about the potential phototransformation of fluorotelomer compounds in landfill leachates, which can undergo environmental oxidation and produce perfluorocarboxylic acids (PFCAs). This study investigated phototransformation of spiked 6:2 fluorotelomer sulfonate (FTS) (∼ 100 µg/L) in leachate under simulated sunlight, using a metal halide lamp (wavelength, 390 to 750 nm). To understand the effects of nitrate and humic acid (HA), phosphate buffer (pH 7.1) containing nitrate and HA were spiked with 6:2 FTS and irradiated under simulated sunlight for 72 h. Following irradiation, 6:2 FTS and known transformation products (i.e., PFCAs) were quantified in the samples using LC-MS/MS. The results showed that 6:2 FTS was undergoing indirect photolysis in leachate (half-life of ∼ 15 days), suggesting that indirect photolysis of 6:2 FTS is likely a relevant transformation pathway in sunlit aquatic environments. However, the spiked 6:2 FTS did not show any observable decrease in the presence of nitrate and HA over 72 h. Perfluorohexanoic acid (PFHxA) increased in irradiated leachate background samples (without 6:2 FTS spike) suggesting that phototransformation in sunlit leachate could lead to the formation of persistent PFCAs at environmental concentrations of the precursors. Future studies using probe compounds are recommended to better understand the roles of reactive species in phototransformation of 6:2 FTS.

Broad-Spectrum Antimicrobial and Antibiofilm Activity of a Natural Clay Mineral from British Columbia, Canada.

Worldwide increases in antibiotic resistance and the dearth of new antibiotics have created a global crisis in the treatment of infectious diseases. These concerns highlight the pressing need for novel antimicrobial agents. Natural clay minerals have a long history of therapeutic and biomedical applications and have lately received specific attention for their potent antimicrobial properties. In particular, Kisameet clay (KC) has strong antibacterial activity against a variety of multidrug-resistant (MDR) bacterial pathogens in vitro Here, we have extended the known spectrum of activity of KC by demonstrating its efficacy against two major fungal pathogens, Candida albicans and Cryptococcus neoformans In addition, KC also exhibits potent activity against the opportunistic bacterial pathogen Mycobacterium marinum, a model organism for M. ulcerans infection. Moreover, aqueous KC leachates (KC-L) exhibited broad-spectrum antibacterial activity, eradicated Gram-negative and Gram-positive biofilms, and prevented their formation. The mechanism(s) underlying KC antibacterial activity appears to be complex. Adjusting KC-L to neutral pH rendered it inactive, indicating a contribution of pH, although low pH alone was insufficient for its antibacterial activity. Treatment of KC minerals with cation-chelating agents such as EDTA, 2,2'-bipyridyl, and deferoxamine reduced the antibacterial activity, while supplementation of KC-L with these chelating agents eliminated the inhibitory activity. Together, the data suggest a positive role for divalent and trivalent cations, including iron and aluminum, in bacterial inhibition by KC. Collectively, these studies demonstrate the range of KC bioactivity and provide a better understanding of the mechanism underlying its antibacterial effects.IMPORTANCE The escalating emergence of multidrug-resistant (MDR) bacteria, together with the paucity of novel antimicrobial agents in antibiotic development, is recognized as a worldwide public health crisis. Kisameet clay (KC), found in British Columbia (BC), Canada, is a clay mineral with a long history of therapeutic applications among people of the First Nations. We previously reported the antibacterial activity of KC against a group of MDR clinical pathogens. Here, we demonstrate its activity against two major human-pathogenic fungal species, as well as against bacterial biofilms, which underlie many recalcitrant bacterial infections. In these studies, we also identified several geochemical characteristics of KC, such as metal ions and low pH, which are involved in its antibacterial activity. These findings provide a better understanding of the components of KC antibacterial activity and a basis for developing defined preparations of this clay mineral for therapeutic applications.

Effect of substrate concentrations on aerobic biotransformation of 6:2 fluorotelomer sulfonate (6:2 FTS) in landfill leachate.

Biotransformation of 6:2 fluorotelomer sulfonate (FTS) results in the formation of short-chain (C4 - C6) perfluorocarboxylic acids (PFCAs) in landfill leachate. Although leachate substrate concentrations (i.e., organic carbon, ammonia) vary widely, their effects on 6:2 FTS biotransformation and PFCAs formation are unknown. This study investigated the effect of organic carbon and ammonia concentration in 6:2 FTS aerobic biotransformation and PFCA formation in leachate. Biotransformation experiments were conducted with sediment collected from a landfill leachate ditch, to which deionized (DI) water and various amounts of leachate were added. Microbial community analysis using 16S rRNA indicated that while phylum Proteobacteria dominated the bacterial composition throughout the 60 days, Actinobacteria increased with time. Many genera from Proteobacteria and Actinobacteria can synthesize a wide array of enzymes, indicating that these phyla are likely to play an important role in 6:2 FTS biotransformation. Higher biotransformation of 6:2 FTS was observed in leachate-added microcosms (∼21%), compared to DI water microcosm (∼14%), likely reflecting the substrate dependency of 6:2 FTS biotransformation. Substrate limiting conditions in DI water microcosm resulted in slightly greater formation of ∑(C4 - C6) PFCAs (∼14 mol%), compared with leachate added microcosms (10-13 mol%). The findings suggest that dilution of landfill leachate, (e.g., during wet seasons), likely results in reduced 6:2 FTS biotransformation and increased PFCAs formation compared to dry conditions. Observed formation of C7 - C8 PFCAs in the live microcosms suggested that landfills act as secondary sources of legacy PFCAs (e.g., perfluorooctanoic acid) in the environment.

Removal of polycyclic aromatic hydrocarbons from aqueous media using modified clinoptilolite.

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment. In this study, the removal of PAHs from aqueous media was assessed using samples of clinoptilolite, a natural zeolite, pre-treated with 1 mol/L of NaCl, (Na pre-treated clinoptilolite, NC). Samples (10 g) of NC were separately modified with 5, 2, 2, and 20-mmol/L solutions of cetylpyridinium chloride (CPC), didodecyldimethyl ammonium bromide (DDAB), hexadecyltrimethylammonium bromide (HDTMA), and tetramethyl ammonium chloride (TMA) surfactants as potential cost-effective adsorbents. The kinetics, optimal sorbent dosage, and competitive effects were evaluated through batch adsorption tests using deionised water spiked with five PAHs (anthracene (50 µg/L), fluoranthene (100 µg/L), fluorene (100 µg/L), phenanthrene (100 µg/L), and pyrene (100 µg/L)). The surfactant non-modified (NC) and TMA-MC (modified clinoptilolite) exhibited PAH removal of <66% from the spiked concentration in aqueous solution, while CPC-MC, DDAB-MC, and HDTMA-MC achieved removal rates of >93% for the five PAHs after 24 h at a solid:liquid ratio of 1:100. The remaining concentrations of anthracene and fluoranthene were below 3 µg/L, and that of fluorene was <6 µg/L, lower than the water quality criteria of British Columbia, Canada, for protecting aquatic life. However, HDTMA-MC retained >83% of the fluorene. Over 80% of all PAHs were absorbed within 15 min for the CPC-MC and DDAB-MC, and the maximum adsorption was reached in <2 h. Three kinetic models were applied assuming pseudo-first-order, pseudo-second-order, and intra-particle equations, and the results were well-represented by the pseudo-second-order equation. The PAH sorption results indicated that the adsorption mechanism is based on PAH hydrophobicity, and π-π electron-donor-acceptor interaction with surfactant. CPC and DDAB with two long chain hydrocarbons had more PAH adsorption than HDTMA with one, and TMA with no long chain hydrocarbons (DDAB-MC > CPC-MC > HDTMA-MC â‰« TMA-MC > NC). With a solid:liquid ratio of 1:200, over 90%, 80%, and 70% of the anthracene, fluoranthene, and pyrene were adsorbed by the CPC-MC, DDAB-MC, and HDTMA-MC, respectively.

Aerobic biotransformation of fluorotelomer compounds in landfill leachate-sediment.

Consumer products containing fluorotelomer polymers are a source of fluorotelomer compounds to the environment following their disposal at landfills. The fate and transformation of fluorotelomer compounds are unknown in landfill leachates. This study investigates the aerobic biotransformation of 8:2 fluorotelomer alcohol (FTOH) and 6:2 fluorotelomer sulfonate (FTS) in landfill leachate-sediment microcosms using batch tests. Spiked 8:2 FTOH, 6:2 FTS and their known biotransformation products were quantified in sediment-leachate and headspace over 90 days under aerobic conditions. 8:2 FTOH and 6:2 FTS biotransformation was slow (half-life >>30 d) in landfill leachate-sediment microcosm, suggesting persistence of fluorotelomer compounds under the conditions investigated. Significant volatilization (>20%) of 8:2 FTOH was observed in the microcosm headspace after 90 days. C6 - C8 and C4 - C6 perfluorocarboxylic acids (PFCAs) were the most abundant products for 8:2 FTOH and 6:2 FTS, respectively. PFCAs accounted for 4-9 mol% of the initially spiked parent compounds at 90 days. Perfluorooctanoic acid (PFOA) was the single most abundant product of 8:2 FTOH (>2.8 mol% at 90 days). The unaccounted mass (20 to 35 mol%) of the initially spiked parent compounds indicated formation of fluorotelomer intermediates and sediment-bound residue. Overall the findings suggest that aerobic biotransformation of fluorotelomer compounds acts as a secondary source of long- and short-chain (≤C7) PFCAs in the environment. Partitioning of semi-volatile fluorotelomer compounds (e.g., 8:2 FTOH) to the gas-phase indicates possible long-range transport and subsequent release of PFCAs in pristine environments. Short-chain fluorotelomer replacements (e.g., 6:2 FTS) result in a higher abundance of short-chain PFCAs in landfill leachate. Future research is needed to understand the long-term exposure effects of short-chain PFCAs to humans, aquatic life and biota.

Formation of perfluorocarboxylic acids from 6:2 fluorotelomer sulfonate (6:2 FTS) in landfill leachate: Role of microbial communities.

Fluorotelomer compounds in landfill leachate can undergo biotransformation under aerobic conditions and act as a secondary source of perfluorocarboxylic acids (PFCAs) to the environment. Very little is known about the role of various microbial communities towards fluorotelomer compounds biotransformation. Using an inoculum prepared from the sediment of a leachate collection ditch, 6:2 fluorotelomer sulfonate (6:2 FTS) biotransformation experiments were carried out. Specific substrates (i.e., glucose, ammonia) and ammonia-oxidizing inhibitor (allylthiourea) were used to produce two experimental runs with heterotrophic (HET) growth only and heterotrophic with ammonia-oxidizing and nitrite- oxidizing bacteria (HET + AOB + NOB). After 10 days, ∼20% of the spiked 6:2 FTS removal was observed in HET + AOB + NOB, compared to ∼7% under HET condition. Higher 6:2 FTS removal in HET + AOB + NOB likely resulted from ammonia monooxygenase enzyme that catalyzes the first step of ammonia oxidation. The HET + AOB + NOB condition also showed higher PFCA (C4-C6) formation (∼2% of initially spiked 6:2 FTS), possibly due to higher overall bioactivity. Microbial community analysis through 16s rRNA sequencing confirmed that Proteobacteria and Bacteroidetes were the most abundant phyla (>75% relative abundance) under all experimental conditions. High abundance of Actinobacteria (>17%) was observed under the HET + AOB + NOB condition on day 7. Since Actinobacteria can synthesize a wide range of enzymes including monooxygenases, they likely play an important role in 6:2 FTS biotransformation and PFCA production.

Simultaneous removal of polycyclic aromatic hydrocarbons and heavy metals from natural soil by combined non-ionic surfactants and EDTA as extracting reagents: Laboratory column tests.

Simultaneous removal of three polycyclic aromatic hydrocarbons (acenaphthene, fluorene and fluoranthene) co-existing with three heavy metals (Ni, Pb and Zn) in artificially contaminated soil from the vicinity of an oil refinery was examined by column flushing of solutions containing Triton X-100 + Ethylenediaminetetraacetic acid (EDTA) and Tween 80 + EDTA at three levels of surfactant concentrations. While the effectiveness of both combined solutions in removal of heavy metals did not differ significantly, Triton X-100 + EDTA was more efficient in removing PAHs. Results showed that after 21 pore volume flushing of enhancing solution (Triton X-100 7.5% + EDTA 0.01 M) at flow rate of 0.534 mL min-1 through the column with hydraulic conductivity of 8.5 × 10-5 cm s-1, 54, 47 and 40% of acenaphthene, fluorene, and fluoranthene were removed simultaneously. At the same conditions, 75, 85 and 90% of Pb, Ni and Zn, were also simultaneously removed. Increasing the flow rate of flushing solution decreased the removal efficiency of the contaminants.

Effect of polybrominated diphenyl ethers on sand-bentonite liner material.

Polybrominated diphenyl ethers (PBDEs) are present in biosolids and other solid wastes, as well as being detected in landfill leachates. As sand-bentonite mixtures are extensively used as basal liner materials for landfills, a sand-bentonite mixture was investigated by swelling tests and leaching column tests to determine whether it can effectively contain and/or immobilize PBDEs in landfill leachate. Leaching column tests were conducted with permeants consisting of biosolids' leachates diluted to 50% by volume and spiked with 50 µg/mL of a pentaBDE mixture solution. The results showed that the sand-bentonite retained up to 45-66% of the total PBDEs in the permeant; however, the concentration of PBDEs in the effluent increased continuously and reached a significant level during a 3-week period. PBDEs probably sorbed onto both fine and ultra-fine organic particles. During leaching, a compacted sand-bentonite admix could stop fine particles from passing, but at the same time, ultra-fine organic particles carried PBDEs through the barrier materials. The hydraulic conductivity, k, of the sand-bentonite was negatively affected by shrinkage of the clay interlayer caused by the permeant hydrophobicity. However, the hydraulic conductivity changed only to a limited extent, remaining at a magnitude of 10-9 cm/s, probably because the PBDE concentrations were low. Therefore, caution is needed when sand-bentonite is applied to landfill liners as a barrier for PBDEs.